The present invention relates generally to a lead assembly for the electrodes of an implantable electrical pulse generator delivering stimulating pulses to an internal organ, and more specifically to such a lead assembly which retains a conductor means therewithin, and is provided with a conductive encapsulating tube which will provide electrical continuity and continued conductivity for the assembly in the event of rupture or severance of the conductors. More specifically, the conductive encapsulating tubular element provides both electrical back-up and a compressive force to grip the conductor means therewithin and reduce the extent of migration of the free ends of fractured wires.
In the design of implantable lead assemblies for delivering stimulating electrical pulses from a pulse generator to an internal organ, such as, for example, a cardiac pacer device or the like, the lead assembly must be sufficiently flexible so as to accommodate flexure at a rate, for example, the normal 72 beats per minute of the human heart. In the past, various types and combinations of conductor means have been employed, and in particular a coiled lead wound in the form of a helix has been widely used. These leads are normally metallic conductors, and have been fabricated from stainless steel such as MT 35 stainless. This material is sufficiently flexible so as to permit its use in implanted lead assemblies.
As has been indicated, and recognized in the art, implantable leads must be sufficiently flexible so as to not interfere with the normal function of delicate systems within the patient. At the same time, these leads must be sufficiently durable so as to withstand substantially constant flexural motion, while, at the same time, withstanding such flexural motion at localized zones or areas along the extent of the lead. Upon occasion, the conductor system may become separated due to fracture, and when this occurs in the assembly of the present invention, conductivity continues by virtue of a conductive sleeve which is arranged to compressively grip the coiled conductors. The structure of the present invention provides an electrically conductive path which is designed so to not be adversely affected by those same forces which tend to either damage or destroy the continuity of the metallic conductor.